This invention relates to a semiconductor integrated circuit tester with an interchangeable tester module.
A semiconductor integrated circuit (IC) tester for testing on a production scale may include a host computer, a test head and a manipulator for positioning the test head at a desired location and orientation for docking to a wafer prober or a device handler. The test head comprises a chassis that accommodates multiple pin electronics cards. Each pin electronics card implements multiple tester channels, each having an I/O terminal. The I/O terminals of the tester channels are connected through a test head interface structure to contact pads on one side (the tester side) of a DUT board. Corresponding pads on the opposite side (the DUT side) of the DUT board are connected to respective pins of sockets for receiving packaged units of a device (in the case of the tester being used with a device handler) or to pins of a probe card (in the case of the tester being used with a wafer prober).
The structure of a pin electronics card depends on the nature of the test being performed at the I/O terminals of the channels that are implemented on the particular card. Typically, a given pin electronics card may be a digital card for digital testing or a mixed signal card for testing with both digital and analog signals. In the event that a tester that has been used for testing units of a given product is to be used for testing units of a different product, it may be necessary to remove several cards from the test head chassis and replace them with other cards. Generally, the resources that have been removed from the test head chassis will remain idle until they are once more installed in the test head chassis.
Another type of IC tester is known as a personal tester. A personal tester may be used by an engineer for testing a single unit of a product, rather than in a production environment. The personal tester is somewhat similar in its basic architecture to the production tester, in that the personal tester comprises a chassis that accommodates multiple pin electronics cards. However, the DUT board of the personal tester may interface directly to the pin electronics cards rather than through a separate interface structure. Typically, a personal tester has more limited capabilities than a production tester. For example, the personal tester may be configured for digital testing or for mixed signal testing but in the event that it is configured for mixed signal testing its capabilities for digital testing are rather limited.
The test head of the conventional production tester is typically supported by the manipulator by means of two stub shafts that project from the chassis through respective side walls of the test head and are received in bearings that are attached to respective arms of the manipulator. The test head can then be turned relative to the manipulator arms by pivoting about the common axis of the stub shafts. A clamp secures the test head in a desired orientation about the pivot axis relative to the arms of the manipulator. A technician can release the clamp, turn the test head about the pivot axis to a desired orientation, and then engage the clamp once again. Let us assume for the purpose of the following discussion that the axis of pivotal movement is horizontal since pivotal movement about a horizontal axis will be sufficient to illustrate the invention. However, it will be appreciated that, in general, the pivot axis need not be horizontal and that the manipulator allows movement of the test head in other degrees of freedom.
In the conventional tester, the shafts are positioned generally centrally in the opposite side walls of the tester, and in the conventional tester the center of gravity of the test head is not necessarily close to the axis of pivotal movement. The torque required to hold the test head at a particular orientation about the pivot axis will vary depending on the orientation of the test head and will be a maximum when the center of gravity of the test head is at the same height as the axis of pivotal movement of the test head. The clamp must be designed to restrain movement of the test head against the maximum torque that may be exerted by the test head, and since the test head itself is heavy, the maximum torque may be substantial. Further, when the clamp is released, the torque exerted by the test head may cause the test head to turn suddenly about the pivot axis and this may pose a danger of injury to the technician.
The host computer is connected to the test head through cables that enter the test head through one or both of the side walls. In addition, power cables pass through one or both side walls of the test head. It is important when turning the test head about the pivot axis to avoid interference between the cables and the arms of the manipulator, since this could lead to damage to the tester.